Veterinary/zoology session

Canine distemper virus (CDV) is a member of the genus Morbillivirus of the family Paramyxoviridae that causes severe multisystemic fatal disease in dogs and many other receptive carnivores. CDV has a wide host range and a worldwide distribution. Previous genetic studies have demonstrated that the genetic diversity of CDV strains has a geographic pattern, and based on the phylogenetic clustering of these strains six lineages can be distinguished: America 1, America 2, Asia 1, Asia 2, Arctic and European. The aim of the present study was to determine the genetic diversity of Hungarian CDV strains and to determine whether more than one genotype is currently present, by analyzing the nucleic acid sequences of the hemagglutinin (H) and fusion (F) genes, which based on previous findings turned out to be suitable to investigate genetic relationships among CDV strains.

A total number of 13 samples collected from 2004 to 2006 from different parts of Hungary were analyzed. The dogs from which the samples were taken had various clinical backgrounds and mostly unknown immunization histories. The samples consisted of urine, blood, nasal swabs and various tissue samples. Some of the samples were collected from the Dog Shelter of the City Council of Budapest in two different periods: in the spring of 2005 and during the spring and summer of 2006. For the analysis of the samples reversed transcription and amplification were preformed in a continuous RT-PCR method. The obtained sequences were compared to other sequences deposited in the GenBank, and a phylogenic analysis was also preformed.

All PCRs performed with newly designed “phylogenetic” primers resulted in amplicons of the expected size, without the presence of any products of nonspecific sizes. The genetic analysis based on the nucleic acid sequence of the H and F genes of the Hungarian strains revealed the presence of more than one cluster of CDV in a geographically small country such as Hungary. Similar situations have been reported in other European, Asian and American countries as well. There are several possible explanations for this finding, such as the increasing trading with receptive species and the uncontrolled movement of animals across borders in recent times. Furthermore, the results emphasize the presence of an endemic infection at the investigated shelter establishment, as well as the seemingly stable genetic change of the virus over a one year period of time. The study also reveals the reservoir role of wildlife for CDV.